The present invention relates generally to a drive system and more particularly to a pump drive and support structure.
Wet clutch assemblies, which are clutches that use oil to cool and lubricate the clutch plates, are known in the art. Wet clutches are commonly positioned between an input device, such as an engine, and an output device, such as a transmission to engage/disengage the output device from the input device. Wet clutches are generally pressure engaged and spring disengaged for high horsepower applications or spring engaged and pressure disengaged for lower horsepower applications.
Gerotor pumps are commonly used with wet clutches to supply the hydraulic fluid needed for cooling, lubrication and pressure engagement/disengagement of the clutch. Gerotor pumps typically include internally toothed and externally toothed gear members rotatably disposed within a pump housing. The gear members are generally coupled to the input device in such a way as to rotate in proportion to the speed of the input device. A first gear member, or pinion gear, typically rotates on a longitudinal centerline common to the centerline of the clutch and pump itself. A second gear member, or ring gear, typically rotates on a longitudinal centerline parallel, but laterally separated from the centerline of the pinion gear. In this manner, the teeth on the respective gear members cooperate to define a plurality of variable volume pumping chambers. During rotation of the gear members, a pumping chamber increases in volume to a maximum volume and then decreases in volume. Fluid from the inlet port of the pump is drawn into the pumping chambers that are increasing in volume. Upon further rotation of the gerotor when the pumping chambers are decreasing in volume, the fluid is pushed out through the outlet port of the pump at a higher pressure.
In a conventional design, a gerotor pump is connected to the clutch assembly such that the rotation of a clutch input member provides rotational power to drive the pump. In this particular configuration, the pump is concentrically aligned in direct rotative connection with the wet clutch assembly. The connection is typically accomplished via the engagement of mating splined surfaces located on a clutch armature and the first gear member of the pump. In this manner, the pump is operational upon activation of the input device to immediately supply hydraulic fluid to the clutch. During operation of the pump, radial loads are generated by the high fluid pressures created as the volume of the pumping chambers is decreased. The direct splined connection between the clutch armature and pinion gear of the pump induces moment loads on the pinion gear of the pump and limits the ability of the mating components to counteract the radial loads, resulting in premature wear or possible damage to the pumping elements and mating components. The present invention provides an effective pump drive and support device that transfers rotative power between a clutch and a pump without premature wear or possible damage to the pumping elements or mating components.
The present invention provides an innovative drive system that couples a clutch assembly with a pump assembly to provide power to control operation of a clutch.
In accordance with an embodiment of the present invention, a drive system is disclosed that includes a drive coupling rotatably supported on an input shaft. The drive coupling includes a generally cylindrical body having a duct therethrough for receiving the input shaft. A bearing member is disposed in a groove on each end of the drive coupling between the body of the coupling and the input shaft to permit independent rotation of the drive coupling on the input shaft. A thrust washer is disposed on each end of the drive coupling proximate the bearing members to secure the bearing members in each groove. A locking member is preferably provided on both a forward end and a rearward end of the drive coupling proximate the thrust washers to secure the position of the drive coupling on the input shaft. The drive coupling further includes at least two connecting surfaces proximate each end of the body that engage a corresponding connecting inner surface of both an armature of thr clutch assembly and a pinion gear of the pump assembly. Upon activation of an input device, and provided the clutch is xe2x80x9cdisengagedxe2x80x9d, the drive coupling will rotate with the clutch assembly independent of the idle input shaft. The rotation of the drive coupling causes a pinion gear of the pump that is positioned concentric to the input shaft to rotate at a speed proportional to the speed of a clutch armature, thereby permitting operation of the pump. Operation of the pump provides fluid power to cool, lubricate and control operation of the clutch.
The foregoing drive system limits moment loads generated at the connecting surfaces and counteracts radial loads generated by the pumping elements to prevent premature wear or possible damage to the pumping elements and mating components. Moreover, the drive system permits differential rotation between the drive coupling and input shaft. Various additional aspects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.